So, would it be possible for me to modify the code my MPGuino is using? I know you're currently working on modifying the original MPGuino code, but I'm not that great of a programmer. At least, I'm not familiar with Arduino, that is.

Everyone's got to start somewhere. Both rationality checks should be able to be squeezed into the existing 0.86 code without too much fuss, though they'll be effectively hardcoded in. That means that, in order to change the thresholds, changes would have to be made to the modified 0.86 code itself. (My code has an EEPROM parameter associated with each rationality check).

The below code is pasted for reference. Only the boldfaced stuff has to be added into the 0.86 code.